1. Field of the Invention
The present invention relates to an ejector, which is a decompressing means for decompressing fluid, and to a momentum transfer type pump for transferring fluid by an entraining action of entraining hydraulic fluid jetting out at high speed. The present invention is effectively applied to a hot water supply device, a refrigerating machine, an air conditioner for vehicle use, and so forth, in which an ejector is adopted as a decompressing means for decompressing refrigerant and as a pump means for circulating the refrigerant.
2. Description of the Related Art
In the conventional ejector which is a refrigerant decompressing means and a refrigerant circulating means, the flow rate of the refrigerant passing through the ejector is adjusted. For example, this type ejector is disclosed in the official gazette of JP-A-2003-90635.
In this conventional example, in the same manner as that of the first embodiment of the present invention, a variable flow rate type ejector is applied to a cycle (ejector cycle shown in FIG. 1) of a hot water supply device. Therefore, the constitution of the ejector (shown in FIG. 2) is substantially the same as that of the embodiment of the present invention. However, the shape of the tapered portion 50, which is formed at an end portion of the needle 24 on the nozzle 18 side, is different from that of the embodiment of the present invention.
As shown in FIG. 8, the tapered portion 50 of the conventional example is formed with one taper angle θ3. When the needle 24 is displaced in the axial direction R (the upward and downward direction in FIG. 8) of the nozzle by the displacement means, the throat portion 18a can be changed, that is, the degree of opening of the nozzle 18 can be changed, that is, the passage area, in which refrigerant can pass through, can be changed. In other words, it is possible to increase and decrease a flow rate of the refrigerant passing through the nozzle 18.
In the conventional example, when the needle valve 24 is displaced in the refrigerant jetting direction (the downward direction in FIG. 8) R1, the degree of opening of the nozzle 18 is decreased. When the needle valve 24 is displaced in the direction opposite to the refrigerant jetting direction (the upward direction in FIG. 8) R2, the degree of opening of the nozzle 18 is increased.
Due to the foregoing, when the compressor is rotated at high speed, that is, when a quantity of the refrigerant flowing into the ejector is large, it is possible to increase the degree of opening of the nozzle 18 so that a quantity of the refrigerant passing through the nozzle (ejector) can be increased. Accordingly, in the evaporator in the ejector cycle, the refrigerant absorbs a larger quantity of heat, and in the water refrigerant heat exchanger (radiator), a larger quantity of heat can be radiated to hot water to be supplied. That is, it is possible to enhance the heating capacity of heating hot water in the case where a quantity of the refrigerant flowing in the cycle is large.
However, in the ejector of the above prior art, when a change in the throat area with respect to the change in the displacement of the needle 24 is reduced in order to stabilize the operation of the cycle by more precisely adjusting a flow rate of the refrigerant, the taper angle θ3 of the tapered portion 50 is necessarily reduced. In this case, the length of the tapered portion 50 is naturally prolonged.
However, the range, in which the displacement means can displace the needle in the axial direction R, is limited. Therefore, in the case where the taper angle θ3 of the tapered portion 50 is small, it is impossible to fully open the throat area. For the above reasons, especially when a flow rate of the refrigerant is high, the high-pressure-side pressure tends to rise, and it becomes necessary to conduct control so that the number of revolutions per second of the compressor can be reduced.